1. Field of the Invention
The present invention is directed to a brake lining wear sensor and is more particularly directed to a modular progressive brake lining wear and temperature sensor.
2. Summary of the Prior Art
Various brake lining wear detection systems are known in the art. In addition, temperature measurement systems are known. However, few brake lining monitoring systems combine both wear detection and temperature sensing. One such temperature and wear detection technique monitors the resistance of a temperature sensitive resistor yielding a signal which represents the operating temperature of the brake lining so that extreme temperature conditions can be detected and corrective action taken. Once the electrical conductive loop is worn away, an open circuit is detected which signals the need for lining replacement.
One method to detect brake lining employs an embedded conductive wire loop within the brake lining. When the loop is broken and furthermore, when electrical contact is made between the wire loop and a brake drum surface, lining wear out is detected. Another brake wear and temperature measurement system utilizes a plurality of thermo-responsive elements disposed within the brake lining where each element is selectively monitored to determine if abnormal temperatures have been encountered and/or whether the brake lining has worn to such an extent that one or more of the thermally responsive elements have been broken.
A more traditional brake temperature indication means comprises a thermocouple disposed within the brake lining connected to a display means to indicate operating temperature of the brake lining. A similar technique uses a combination temperature and wear sensor disposed in a brake cylinder where the sensor has a slider mechanism that is pressed on the face of a brake cylinder to indicate brake wear and also includes a temperature sensing device thereby indicating the wear of the brake lining and overheating of the brake fluid through a pair of lead out wires.
It is an object of the present invention to provide a dual temperature and progressive break wear sensor in a single compact erodable element.
The present invention is directed to a modular progressive brake lining wear and temperature sensor. The sensor has a plurality of parallel-arranged spaced apart resistors in connection with a sensing circuit. Each resistor mounted onto a PC board which is encapsulated within a single molding. A thermistor is also mounted on the PC board within the molding to sense temperature. The thermistor is connected to a grounded lead as are each of the spaced apart resistors. The ground lead, a resistance lead and a thermistor lead emerge from the encapsulated sensor for connection to a sensing circuit. The sensor is disposed within the brake lining. As the brake lining progressively wears, the resistors are progressively worn away thus changing the overall resistance of the sensor. The change in resistance indicates state of wear. Preferably three resistors are employed to indicate four degrees of brake lining wear. The thermistor indicates brake lining temperature and may be used to balance vehicle brakes.